Cell Cultures and Characteristics Questions and Answers

Q: What is the preparation of Nutrient Agar (NA) in common culture media?

Nutrient agar is made with 0.5% peptone, 0.3% beef extract and 1.5% agar.Nutrient agar is nutrient broth (peptone 0.5%, beef extract 0.3% and usually sodium chloride 0.5%) solidified with about 1.5% agar. Peptone and beef extract supply nitrogen, vitamins and minerals; agar is only a solidifying agent that bacteria do not digest.Peptone water is 1% peptone with 0.5% NaCl, a liquid medium with no agar, which is the second option. The other two mixtures, with 2% or 3% peptone or 2% salt, do not correspond to the standard formula.

Q: Peptone water and nutrient broth are

Correct answer: basal mediaPeptone water and nutrient broth are basal (simple) media: they support the growth of ordinary non-fastidious organisms and serve as the foundation to which blood, serum or inhibitors are added to make enriched or selective media.

Q: A high dissolved oxygen concentration in the culture medium is toxic and leads to

Correct answer: all of the aboveToo much dissolved oxygen generates reactive oxygen species, and all three consequences follow: DNA damage, lipid peroxidation of the membranes, and excessive metabolism of the medium’s nutrients. This is why oxygen is controlled rather than simply maximised in a bioreactor.

Q: Which of the following is used for the proper maintenance and preservation of pure cultures?

Correct answer: All of the aboveAll three are standard. Periodic transfer to fresh medium keeps a culture alive but risks contamination and mutation over many passages. Overlaying with mineral oil slows drying and metabolism, extending the interval between transfers. Lyophilisation - freeze drying - is the best for long-term storage, keeping cultures viable for years with no change.

Q: Which of the following bacteria can grow in alkaline pH?

Correct answer: Vibrio choleraeVibrio cholerae is alkalophilic, growing well up to about pH 9 - which is exploited in alkaline peptone water enrichment. The other three are enterobacteria with neutral optima, and lactobacilli prefer acid.

Q: The medium which allows the growth of more than one microorganisms of interest but with morphologically distinguishable colonies is known as

Correct answer: differential mediumA differential medium lets several organisms grow but makes them look different - through a fermentable sugar and a pH indicator, or through haemolysis on blood agar. A selective medium, by contrast, stops the unwanted organisms growing at all.

Q: Which type of culture is prepared by inoculating directly from the tissue of an organism into culture medium?

Correct answer: Primary cell cultureA primary culture is one started directly from tissue taken from the organism. It most closely resembles the tissue of origin, but has a limited lifespan - once subcultured it becomes a cell line.

Q: In the secondary culture, cells are obtained from _______________________

Correct answer: primary cultureA secondary culture is obtained by subculturing a primary culture - detaching the cells, usually with trypsin, and reseeding them in fresh medium. The organism itself is the source only of the primary culture.

Q: Toxicity due to the accumulation of ammonia can be overcome

Correct answer: all of the aboveAll three help. Substituting glutamate for glutamine removes the amide nitrogen that becomes ammonia; feeding glutamine slowly keeps its concentration low, so less is deaminated; and removing the ammonium as it forms - by dialysis or by ion exchange - deals with what is produced. All are used in high-density culture.

What is the preparation of Nutrient Agar (NA) in common culture media?

A.0.5% peptone, 0.3% beef extract, 1.5% Agar
B.1% peptone, 0.5% NaCl in distilled water
C.2% peptone, 0.6% beef extract, 2% Agar
D.3% peptone, 2% NaCl

Exam Year(s)

RSMSSB - 2025, RSMSSB Lab Technician - 2025,

Answer: A

Nutrient agar is made with 0.5% peptone, 0.3% beef extract and 1.5% agar.

Nutrient agar is nutrient broth (peptone 0.5%, beef extract 0.3% and usually sodium chloride 0.5%) solidified with about 1.5% agar. Peptone and beef extract supply nitrogen, vitamins and minerals; agar is only a solidifying agent that bacteria do not digest.

Peptone water is 1% peptone with 0.5% NaCl, a liquid medium with no agar, which is the second option. The other two mixtures, with 2% or 3% peptone or 2% salt, do not correspond to the standard formula.

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Peptone water and nutrient broth are

A.selective media
B.enriched media
C.basal media
D.none of these

Answer: C

Correct answer: basal media

Peptone water and nutrient broth are basal (simple) media: they support the growth of ordinary non-fastidious organisms and serve as the foundation to which blood, serum or inhibitors are added to make enriched or selective media.

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A high dissolved oxygen concentration in the culture medium is toxic and leads to

A.DNA degradation
B.lipid peroxidation
C.metabolism of nutrients in culture media at a rate greater than that required for consumption
D.all of the above

Answer: D

Correct answer: all of the above

Too much dissolved oxygen generates reactive oxygen species, and all three consequences follow: DNA damage, lipid peroxidation of the membranes, and excessive metabolism of the medium’s nutrients. This is why oxygen is controlled rather than simply maximised in a bioreactor.

Discuss in Forum

Which of the following is used for the proper maintenance and preservation of pure cultures?

A.Periodic transfer to fresh media
B.Preservation by overlaying cultures with mineral oil
C.Preservation by lyophilization
D.All of the above

Answer: D

Correct answer: All of the above

All three are standard. Periodic transfer to fresh medium keeps a culture alive but risks contamination and mutation over many passages. Overlaying with mineral oil slows drying and metabolism, extending the interval between transfers. Lyophilisation - freeze drying - is the best for long-term storage, keeping cultures viable for years with no change.

Discuss in Forum

Which of the following bacteria can grow in alkaline pH?

A.Shigella
B.Lactobacilli
C.Salmonella
D.Vibrio cholerae

Answer: D

Correct answer: Vibrio cholerae

Vibrio cholerae is alkalophilic, growing well up to about pH 9 - which is exploited in alkaline peptone water enrichment. The other three are enterobacteria with neutral optima, and lactobacilli prefer acid.

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The major problem associated with the isolation of free cells and cell aggregates from organs is that of

A.releasing the cells from their supporting matrix
B.inhibiting the cells from their supporting matrix
C.disintegrating the cells from their supporting matrix
D.none of the above

Answer: A

Correct answer: releasing the cells from their supporting matrix

The cells of an organ are held in an extracellular matrix of collagen and other proteins, and the difficulty is freeing them from it without damaging them. Enzymes such as collagenase and trypsin, and chelators such as EDTA, are used for the purpose, and the balance is always between complete release and cell injury.

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The medium which allows the growth of more than one microorganisms of interest but with morphologically distinguishable colonies is known as

A.selective medium
B.enrichment medium
C.differential medium
D.none of these

Answer: C

Correct answer: differential medium

A differential medium lets several organisms grow but makes them look different - through a fermentable sugar and a pH indicator, or through haemolysis on blood agar. A selective medium, by contrast, stops the unwanted organisms growing at all.

Discuss in Forum

Which type of culture is prepared by inoculating directly from the tissue of an organism into culture medium?

A.Primary cell culture
B.Secondary cell culture
C.Cell lines
D.Transformed cell culture

Answer: A

Correct answer: Primary cell culture

A primary culture is one started directly from tissue taken from the organism. It most closely resembles the tissue of origin, but has a limited lifespan - once subcultured it becomes a cell line.

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In the secondary culture, cells are obtained from _______________________

A.primary culture
B.the organism
C.organ culture
D.phenotypic culture

Answer: A

Correct answer: primary culture

A secondary culture is obtained by subculturing a primary culture - detaching the cells, usually with trypsin, and reseeding them in fresh medium. The organism itself is the source only of the primary culture.

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10.

Toxicity due to the accumulation of ammonia can be overcome

A.by substituting glutamine by glutamate
B.by controlled addition of glutamine at low level
C.by removal of ammonia or ammonium from culture medium
D.all of the above

Answer: D

Correct answer: all of the above

All three help. Substituting glutamate for glutamine removes the amide nitrogen that becomes ammonia; feeding glutamine slowly keeps its concentration low, so less is deaminated; and removing the ammonium as it forms - by dialysis or by ion exchange - deals with what is produced. All are used in high-density culture.

Discuss in Forum

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